This study investigated parents' backgrounds and their beliefs about English language learning, and compared the receptive English vocabulary development of three to six year-old-Thai children before and after participating in a parent-child reading program with the dialogic reading (DR) method. Fifty-four single parents of 54 children voluntarily participated in the study. The parents were surveyed to determine if their demographic data, beliefs, and DR method affected their children's vocabulary development. The children were tested on fourteen English words before and after participating in the program. The results showed that parents' beliefs about English language learning affected expectations on their children's language success. In addition, the children's achievement was related to the use of DR method. The children yielded significant greater gains in knowledge of vocabulary and their ability to infer the meanings from pictures after engaging in the reading program.